Regenerated cellulose filaments and products therefrom



R. WOODELL 2,834,093 REGENERATED CELLULOSE FILAMENTS AND PRODUCTS THEREFROM May 13, 1958 Filed May 21, 1954 FIGE FIGIES INVENTOR RUD OL PH WOODELL ATTORNEY REGENERATED CELLULOSE FILAMENTS AND PRODUCTS THEREFROM Rudolph Woodell, Richmond, Va., assignor to E. I. du Pont de Nemours and Compan Wilmington, Del a corporation of Delaware Application May 21, 1954, Serial No. 431,567 6 Claims. (Cl. 28-78) This invention relates to a textile product of regenerated cellulose and, more specifically, relates to the production of regenerated cellulose filaments having a novel configuration which imparts unusual bulk and covering power to yarn and textile fabric made therefrom.

Regenerated cellulose fibers are initially produced as continuous filaments and these can be processed into yarn much more readily than short the naturally occurring fibers, e. g. cotton or wool, which exist in only relatively short lengths. The spinning of yarn from the latter short fibers is time-consuming, requiring a complex series of operations to align the fibers, cobbine them into an elongated bundle, draw the bundle to a smaller diameter while twisting to slippage of adjacent fibers twisting into a yarn suitable for textile purposes.

While the processing of continuous filaments into'yarn eliminates most of these spinning operations and involves only twisting, the yarn is dense than the spun yarn and has less covering power when Woven into fiabric. The filaments lie close together in the yarn and the adjacent strands of fabric are closely spaced. This compactness limits the amount of insulating.- heavier fabric to achieve warmth air space and necessitates and covering power.

The desirable qualities of lightness, covering effectiveness and warmth-giving bulk are ditficult to achieve in textile fabric made from conventional continuous filaments. To achieve these qualitiesin competition with natural fibers it has previously been found necessary to cut continuous filament regenerated cellulose into staple fibers and spin these into yarn by the time-consuming and more expensive methods used for natural fibers. Moreover, this results in and uniformity in the yarn. longer the staple fibers are, the stronger and more uniform the spun yarn will be. The strength of spun yarn depends primarily upon the strength of the individual fibers and secondarily upon the expertness and art of the spinner.

to get uniformity and evenness throughout the length deficient for many textile uses. The conventional continuous filament yarn is much more a sacrifice of strength It is recognized that the fibers, such as staple or I prevent excessive past one another, and finally of the spun yarn. If fibers are broken down-in any of,

the various stages of opening, carding, combing and drawing, the evenness, uniformity and, therefore, the Even under the most quality of the spun yarn suffers. favorable conditions a spun rayon yarn cannot be as uniform as a continuous filament yarn.

The strength of spun yarn approaches but never reaches the fiber strength ofa continuous filament yarn of the same size: There are inveitable variations in the number of fibers at any given cross-section. are definitely more desirable the type noted.

It is an object of this invention to provide continuous filaments of regenerated cellulose which form yarns and fabrics having the advantages of both ordinary continuous filament and spun staple yarns and fabrics withoutthe individual deficiencies each, i. "e., which combine the 2,834,093 Patented May 13, 1958 strength, uniformity and ease of processing of continu Figure 1 is a reproduction of a photomicrograph at 9700 times magnification of a transverse cross-section through several filaments prepared in accordance with this invention, the filaments having beendifferently dyed to distinguish the skin area;

Figure 2 is a corresponding lateral view of a portion of a typical filament, prepared from a photomicrograph at 700 times magnification; and

Figure 3 is a lateral view prepared from a photomicrograph at 50 times magnification of a yarn composed of filaments in accordance with this invention. I

The following additional drawings are of typical prior artfilaments and yarn, and are with the above. These drawings are analogousreproductions of corresponding photomicrographs:

Figure 4 shows a differentially dyed transverse crosssection through the crimped filaments produced in ac cordance with U. S. Patent No. 2,515,834 to W. D. Nicoll and as described subsequently in connection with yarn type B.

Figure 5 shows a similar cross-section through conventional filaments produced from ripened, unmodified viscose described subsequently in connection with yarn type C. I

Figure 6 is a lateral view of a portion of one of the filaments of Fig. 4.

Figure 7 is a lateral view of a portionof atypical yarn composed of filaments prepared in accordance with U. S. Patent No. 2,515,834.

The present invention provides a novel filament which differs markedly from previous regenerated cellulose filaments in having an unusually rough or scaly surface, as will be observed from a comparison of the figures. When'viewed under high magnification, as in Fig. 2, the scaly surface is seen to consist of minute'wave-like irregularities of the order of 200-700 waves per inch along the length of the filament. The filaments also crimp when relaxed to the appearance shown in Fig. 3. This crimp is of low amplitude, as compared with the crimp obtained in accordance with U. S. Patent No. 2,515,834

and shown in Fig. 4, but is irregular and of quite high of this invention have the warmth-giving bulk, high covering power, surface roughness and broadcloth appearance previously achieved onlyv with spun staple. On the other hand, the desirable strength of prior art continuous filaments is retained and the flex life is actually improved by 1% to 3 times. The unique crimp of these filaments becomes apparent from a comparison of Figs. 3 and 7. In the latter the marcel-like, in-phase crimp, plus the smooth surface of the filaments, has resulted in a close packing of the filaments so that, although the crimp is of relatively high amplitude, the filaments are essentially parallel to each other.

portion of a typical provided for comparison keeps the filaments spaced apart The filaments of this invention are produced by a process which, briefly, comprises the steps of extruding a viscose containing 4 to 8% NaOH and 5 to 7% (based on the cellulose content) of a cellulose xanthate prehaving a sulfuric acid content in'the range of 8 to 13%, which is above the acidity at the minimum gel swelling factor and which gives a gel swelling factor of 3 to 5,-a

sodium sulfate content of 12 to 22% and a zinc sulfate content of 6 to 15% to form filaments, stretching the filaments at least prior to complete regeneration and, after at least substantially complete regeneration, relaxing the filaments in a swelling medium. The viscose solution may contain from 0 to 1% by weight of a moditier of the type disclosed in the application of N. L. Cox and W. D. Nicoll, filed on the same day as the present application, and from 0.05 to 1% is required when the cellulose content of the viscose is in the high rangeof 6.5, to 7%, or when the cellulose xanthate is prepared with 33 to of carbon disulfide. The process works particularly well in the production of continuous filaments of 3 to 10 denier in accordance with this invention.

The viscose solution may be prepared in the usual manner by xanthating alkali cellulose with 20 to 45% carbon disulfide and diluting with water and caustic to give a viscose of the specified composition.

The viscose spinning solution is extruded in the conventional manner into a spinning bath containing 8 to 13% sulfuric acid and 12 to 22% sodium sulfate. For the purpose of this invention, it is absolutely essential that the bath also contain at least 6% zinc sulfate, pref: erably about 9.5% zinc sulfate. 1 have also found it necessary to adjust the acid content so as to be above the acidity at the minimum gel swelling factor and provide a gel swelling factor for theunstretched yarn of 3 to 5.

Gel swelling factors are determined as described in U. S. Patent No. 2,515,834 to W. D. Nicoll, and the minimum factor may be determined from a curve of the type shown therein.

The spinning bath. is preferably, maintained at a lGIHt' perature of 40-75 'C.' The distance which the filaments travel through the spinning bath will vary with the speed of spinning. It has been found that both travel distances from 10 to over inches and as high as 150v inches are operable.

This process requiresthata stretch of at least 40% be imposed upon the filaments. This stretch maylbe ap: plied to the filaments in'the spinning bath by using conv. ventional rotary or stationary tension rollers. Alter:

natively this stretch may be applied in a separate sec.

ondary bath or the stretch may be partially appplied in the spinning bath and completed in separate secondary bath and/or between two or more feed wheels.

The filaments may be collected prior to purification on a bobbin or in a bucket and be purified batch-wise. Alternatively the yarn may be purified by applying treating liquids directly to helical windings of the yarn on advancing reels or in any other continuous process. Optimum crimpability can be obtained by stretching the.

purified yarn and drying it under tension. The filaments.

in a solution at room temperature is susually s'ufficient.

The only requirement is thatthe' The following examples illustrate the process of this:

invention, but are not to be construedas limitative.

EXAMPLE I y A viscose spinning solution containing 7% by weight in-bath roller guides.

the filaments were at a tension of 0.7 gram per denier.

. h aves cellulose, 6% by weight sodium hydroxide and 0.2% by weight cyclohexylarnine was prepared from wood pulp in the usual manner, using 23% Carbon disulfide (based on the weight of air-dried pulp). This solution, at a salt index of 3.3 was extruded through a spinneret into a spinning bath at 60 C. containing 11.5% H 50 17.5% Na SO and 9.5 ZnSO The filaments were led through 44 inches of bath by appropriately arranging the Upon emergence from the bath.

The gel swelling value of the unstretched yarn was 4.0. After leaving the bath the filaments passed over two feed wheels having a differential in speed sutlicient to stretch the filaments 77%. During this stretching operation, the filaments were treated with hot, very dilute spinning bath. Spinning occurred at a speed of 100 yards per minute and the resulting filament size was three denier.

The yarn was collected on a rotating bobbin to form a cake. 5 The cake was purified in the conventional manner. After purification, the cakes were wound into skeins. As skeins the yarn was immersed, while com pletely free to relax, in a solution of 3% sodium hydroxide at about 27 C. for about 4 minutes. The skeins were then dried without tension. The resulting filaments averaged above 40 crimps per inch.

EXAMPLE II A viscose spinning solution containing 6.25% by weight cellulose, 5.4% by weight sodium hydroxide, 0.2% by weight 'cyclohex-ylamine was prepared from wood pulp, using 33% carbon disulfide (based on the weight of air dried pulp). This solution, at a salt index of 10.2, was extruded through the spinneret into a spinning bath at 60 C. containing 1010.S% H SO ,17.5% N21 SO 9.5% ZnSo and 0.13% cyclohexylamine. The filaments were led through 44 inches of bath by appropriately arranging thein-bath roller guides. Upon emergence from the bath, the filaments were at a tension of 0.7 gram per denier. -The gel swelling value of the unstretched yarn ranged from 3.0 to 4.9. After leaving the bath the filaments passed over two feed wheels having a differential in speed sufficient to stretch the filaments 101%. During the stretching operation, the filaments were treated with .manner described in Example I. The resulting filaments averaged above 40 crimps per inch.

EXAMPLE III A viscose spinning solution containing 5.5% by weight of cellulose and 5.5% by weight of sodium hydroxide was prepared from wood pulp, using 33% carbon disulfide (based on the weight of air-dried pulp). This solution, at a salt index ofl2.0, was extruded through a spinnerct into a spinning bath at 60 C. containing 10% H 80 17.5% NaSO and 9.5% ZnSO The filaments were led through inches of bath and stretched by appropriately arranging the ii -bath roller guides. Upon emergence frornthe bath, the filaments were at a tension of 0.3 gram per denier. The gel swelling value of the unstretched yarn was 3.1. After leaving the bath the filaments passed over two feed wheels having a dirferential A viscose spinning solution containing 5.0% by weight cellulose. and 4.3 by weight sodium hydroxide was pre'-.

pared from wood pulp, using 33 carbon disulfide (based on the weight of air-dried pulp). This solution, at a salt index of 13.1, was C'itl'lldfid through a spinneret into a spinning bath at 60 C. containing 7.5% H 50 17.5% Na SO and 9.5% ZnSO The filaments were led through 44 inches of bath and stretched by appropriately arranging the in-bath roller guides. The filaments emerged from the bath at a tension of 0.4 gram per denier. The gel swelling value of the unstretched yarn was 4.2. Spinning speed after a stretching was 100 yards per minute and the resulting filament size was 3 denier.

The yarn was collected, purified and crimped in the manner described in Example I. The resulting filaments averaged above 40 crimps per inch.

EXAMPLE V A viscose spinning solution containing 6.25% by weight of cellulose, 5.4% by weight of sodium hydroxide, and 0.2% by weight of cyclohexylamine was prepared from wood pulp using 33% carbon disulfide (based on the weight of air-dried pulp). This solution, at a salt index of 10.3, was extruded through a spinneret into a spinning bath at 60 C. containing 9-9.5% H 80 21% Na SO 6% ZnSO The filaments were led through 44 inches of bath by appropriately arranging the in-bath roller guides. The gel swelling value of the unstretched yarn was 3.8. passed over to the feed wheels having a differential in speed sufficient to stretch the filaments 100%. The ten- After leaving the bath, the filaments were sion between the feed wheels was 0.7 g. p. (1. During thestretching operation, the filaments were treated with hot, very dilute spinning bath. Spinning occurred at a speed of 100 Y. P. M. and the resulting filament size was 3 denier.

The yarn was collected on a rotating bobbin to form a cake. The cake was purified in the conventional manner. After purification, the cakes were wound into skeins. As skeins the yarn was immersed in a completely free-to-relax condition in a solution of 3% sodium hydroxide at about 27 C. for about 4 minutes. The skeins were then washed free of sodium hydroxide and then dried without tension. The resulting filaments averaged over 40 crimps per inch.

of 100' Y. P. M., and the resulting filanient'size was 3 denier.

The yarn was collected on a rotating bobbin to form a cake. The cake was purified in the conventional manner. After purification, the cakes were wound into skeins.

As skeins the yarn was immersed in a completely freeto-relax condition in a solution of 3% sodium hydroxide I The skeins were EXAMPLE VII A viscose spinning solution containing 6.25% by weight cellulose and 5.4% by weight sodium hydroxide was prepared from wood pulp, using 28% carbon disulfide (based on the weight of air-dried pulp). This solution, at a salt index of 7.2, was extruded through a spinneret into a spinning bath at C. containing 10.0% H 17.5% NaSO and 9.5% ZnSO were led through 44 inches of bath by appropriately arranging the in-bath roller guides. Upon emergence from the bath, the filaments were at a tension of 0.63 gram per denier. stretched yarn was 3.2. After leaving the bath the filaments passed over two feed wheels having a difierential in speed sufiicient to stretch the filaments During this stretching operation, the filaments were treated withhot, very dilute spinning hath. Spinning occurred at a speed of 100 yards per minute and the resulting filament size was 3 denier.

The yarn was collected, purified and crimped in the manner described in Example I. The resulting filaments averaged above 40 crimps per inch.

Yarn and fabric composed of the filaments of this invention will now be compared with ones composed of typical filaments of the prior art.. In the following tables. yarn type A is composed of the filaments'of Example VII and as shown in Figs. 1, 2 and 3, yarn type B'is composed'of typical crimped filaments of the type shown in Figs. 4, 6 and 7, and conventional uncrimped filaments of the type shown in Fig. 5. Table I summarizes the important spinning conditions used in preparing the three types of filaments.

Table I.Summary of process conditions Viscose Spin Bath Spinning Yarn Tension Gel Relaxing Type Spinning Set Up (rms./ Swelling Medium.

Percent Percent Percent Percent Percent Percent Percent denier) Value cell. NaOH CS H 50 Na2S04 ZnSOr Glucose I A 6.25 5.4 28 10.0 17.5 9.5 0 100%; sltretch between feed 0.63 3.2 3% NoOH w ee s. B 7.00 6.0 30 8.4 24.0 1.5 4.0 Stretched in spin bath by 0.67 15% NaOH tension rollers. C 7. 00 6.0 30 11.0 19.75 0.7 2.0 Stretched in spin bath by 0.20 3.5 5% NaOH tension rollers.

EXAMPLE VI The subsequent tables present the important prop- A viscose spinning solution containing 6.25% by weight of cellulose, 5.4% by weight of sodium hydroxide, and 0.2% by weight of cyclohexylamine was prepared from wood pulp using 33% carbon disulfide (based on the weight of air-dried pulp). This solution, at a salt index of 9.9, was extruded through a spinneret into a spinning bath at 60 C. containing 9.5 to 10.5% H 80 19% Na SO 7.5% ZnSO The filaments were led through 44 inches of bath by appropriately arranging the in-bath roller guides. The gel swelling value of the unstretched yarn was 3.6. After leaving the bath, the filaments were passed over two feed wheels having a difierential in speed sufiicient to stretch the filaments The tension between the feed wheels was 0.6 g. p. d. During the stretching operation,.the filaments were treated with hot,

very diulte spinning bath. Spinning occurred at a speed A erties of the above three continuous filament yarns, A,

B, and C, and some of the properties of staple yarns- D and E. Yarn D is composed of staple prepared from. yarn B. Staple yarn E is similarly prepared from yarn The sample, supporting a 0.15% gram/denier load, is.

The filaments The gel swelling value of the-unyarn type C is composed of gear reducer, driven fiexed through an angle of about 265 at a rate of 123 flexes per minute. The edges of the blades are in the exact center of rotation in order to keep the thread from swinging back and forth during flexing. The filament is flexed until it breaks. When it breaks, the small metal weight falls into a metal trough below the fiexer blades and closes an electrical circuit, which in turn stops the motor. The flex number may be observed on the counter. A high flex number has been found to indicate that the filament, and yarn produced from such filaments, will display a high resistance to abrasion and improved launderability properties.

Table II.Yam physical properties The yarn of this invention, type A, has not only retained the desirable strength and elongation properties of the conventional uniform continuous filament yarn, type C, but in addition, it will be observed that the flex life is improved from 1 /2 to 3-fold over the comparative continuous filament yarns.

In Table III, the properties of the various fabrics are presented. The bulk (em /gm.) is determined by dividing the thickness (cm.) by the weight per unit area (gm/cm?) of the fabric. The bulk-firmness, measured in glll.-I1'llll., correlates with the drape and hand of a fabric. It is proportional to the bending length and the flexural rigidity (W). The bending length is the length of a strip of fabric required as a horizontal cantilever to cause the strip to bend, under its own weight, to an angle of 45 with the horizontal. A high bending length indicates good shape retention. The flexural rigidity is the moment of the couple required to bend a strip of fabric of unit width to a circle having a radius of l centimeter. In other Words, it is composed of the pair of counteracting forces that would be felt as pressure on the skin if a strip were bent between a finger and the thumb. Flexural rigidity increases as the firmness of hand of the fabric increases. Bulkfirmness (gm.- rnm.)=W(gm./mm. .C (mmfi). The underlying principles of the bulk-firmness test were developed by F. T. Pierce in his hanging heart test, Journal of the Textile Institute, vol. 21 (1930) pp. T377-T4l6.

Table [IL-Fabric properties The improvement in bulk of the fabric prepared from the yarn of this invention ranges from 50% over fabrics prepared fromstandard continuous filament yarns and staple yarn. To obtain acceptably high bulk with standard yarns, the end count can be reduced. However, when this is done a loss in firmness and fabric stability inevitably follows.

The bulk firmness of fabric from yarn A has been compared to yarns B and C separately at two different bulk values. It will be observed that increasing the bulk of yarn A from 2.30 to 3.20, accomplished by reducing end count, results in the previously-mentioned loss in firmness. The results of Table III show that, at equivalent bulk, the firmness of yarn A fabric is about 33% higher than the other continuous filament fabrics.

In Table IV, available data are presented comparing the covering power of fabrics from continuous filament yarns. Results of tests measuring the wet flex fabric abrasion are also presented. This latter is the Stoll test. It measures the durability of wear resistance of fabrics. Details of the test may be found in R. G. Stolls article in Textile Research Journal, vol. 19 (1949), p. 394.

n The covering power is measured by the amount of light transmitted through the fabric, recorded as microamperes. The lower the value, the less light transmitted through the fabric and hence, the greater the covering power.

Table I V.Fabric properties Covering Power (microumperes) Wet Flex Abrasion Yarn Type High End Count Low End Count Fabric (cycles to failure) Twill Plain Twill Plain Weave Weave Wear Weave YarnA averages covering power values 31% greater than yarn B and 56% greater than yarn C. The wet fiexfabric abrasion test provides a remarkable result. Yarns having uneven surfaces usually show poorly on the Stoll tester. For example, the uneven surface of spun yarn, yarn E, produces a test result about 40% of the result obtained with standard viscose yarn, yarn C. However, the rough surface of yarn A does not produce this poor result. Instead, an improvement of over standard yarn is obtained.

From a study of the complete results, it is evident that the yarn of this invention has retained the desirable strength and elongation properties of continuous filament yarns. Its fiex life has improved 1.5 to 3-fold over other continuous filament yarns. Despite overall improvement in physical properties, this yarn has also acquired the bulk and covering power of a spun staple yarn. However, as a continuous filament yarn, the yarn does not become uneven or acquire any of the inherent, undesirable variations of a spun staple yarn.

In fabric form, the yarns of this invention provide high strength, high bulk, a spun-like surface roughness, low luster, a pleasing broadcloth appearance, high covering power and improved wrinkle-resistance. The high bulk of the fabric may be attributed to (1) high, out of phase crimp of the individual filaments and (2) the rough surface of the filaments. The rough surface of the filaments seems to prevent filaments from lying as close to adjacent filaments as in the shiny fabrics made from smooth standard viscose rayon filaments. It is postulated that interlilament cohesion cannot occur as easily with the rough surface filament as with a smooth surface filament. Hence, the filaments do not pack together as tightly. However, despite its rough surface, a fabric made from this yarn displayed surprisingly high resistance to wet flex fabric abrasion on the Stoll tester.

There are many other advantages. This yarn has the most desirable properties of a spun staple yarn, yet it is produced without cutting continuous filament yarn and reforming a yarn from the cut, staple fibers. The yarn is economically prepared by the conventional necessary, but the basic raw materials and procedural steps remain the same.

This yarn is sufiiciently uniform to be handled easily by textile machinery and to form highly uniform fabrics without sacrificing the bulk or acquiring the undesirable characteristics of fabrics made from mechanically crimped yarns. The yarn can be used without difficulty on both automatic weaving and automatic knitting machines. The increased covering effectiveness and strength of fabric made from this yarn permit the production of more fabric from the same weight of yarn. In addition, this yarn can replace expensive or scarce fibers in many uses.

If desired, this yarn can be processed into staple fibers and formed into a spun yarn for use either alone or as a blending fiber with wool, cotton or man-made staple or continuous fibers. As a staple fiber, its covering power and bulk properties are even greater than in the form of continuous filament. The staple fibers may be prepared by conventional methods from the continuous filaments described herein, and are preferably prepared before the filaments are crimped in a relaxing bath. As an illustration of the process, filament bundles proceeding from several spinnerets may be combined into a tow. After the usual liquid treatments the wet tow is fed to a conventional staple cutter and cut into staple fibers. These fibers may be allowed to fall into a relaxing bath, which will cause the fiber clumps to open in addition to crimping the fibers. The relaxing bath may also replace one of the liquid treatments, such as washing or desulfuring, and thus accomplish two purposes.

Since many difierent embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

What is claimed is:

l. A regenerated cellulose filament having a rough surface comprising wave-like irregularities of the order of 200 to 700 per inch along the length of the filament.

2. A regenerated cellulose filament having a rough surface comprising wave-like irregularities of the order of 200 to 700 per inch along the length of the filament, said filament having the property of spontaneously crimping, upon being suspended free of tension in an aqueous liquid, to an irregular crimp.

3. A crimped regenerated cellulose filament having a rough surface comprising wave-like irregularities of the order of 200 to 700 per inch along the length of the filament, said filament having in addition an irregular crimp, amounting to over 40 crimps per inch.

4. A yarn composed of crimped filaments of regenerated cellulose having rough surfaces comprising wavelike irregularities of the order of 200 to 700 per inch along the filaments, said filaments having irregular crimps, amounting to over 40 crimps per inch, the crimps of adjacent filaments being out of phase and keeping the filaments spaced apart, thereby providing high bulk.

5. A yarn composed of filaments of regenerated cellulose having rough surfaces comprising wave-like irregularities of the order of 200 to 700 per inch along the filaments, said irregularities being of such size as to prevent close packing of the filaments and to provide a low luster.

6. A textile fabric composed of crimped filaments of regenerated cellulose having rough surfaces comprising wave-like irregularities of the order of 200 to 700 per inch along the filaments, said irregularities being of such size as to prevent close packing of the filaments and impart a low luster and high covering power to the fabric.

References Cited in the file of this patent UNITED STATES PATENTS 2,088,558 Hofmann July 27, 1937 2,249,745 Charch et al July 22, 1941 2,369,395 Heymann Feb. 13, 1945 2,403,437 Kohorn July 9, 1946 2,434,533 Wurzburger Jan. 13, 1948 2,439,039 Coe Apr. 6, 1948 2,443,711 Sisson June 22, 1948 2,491,937 Schlosser et al. Dec. 30, 1949 2,515,834 Nicoll July 18, 1950 2,517,694 Merion et al Aug. 8, 1950 2,572,936 Kulp et al Oct. 30, 1951 2,637,893 Shaw May 12, 1953 2,674,025 Ladisch Apr. 6, 1954 

1. A REGENERATED CELLULOSE FILAMENT HAVING A ROUGH SURFACE COMPRISING WAVE-LIKE IRREGULARITIES OF THE ORDER OF 200 TO 700 PER INCH ALONG THE LENGTH OF THE FILAMENT. 